The file format is 16-bit TIFF.
alb_d.tiff and alb_s.tiff contain diffuse and specular albedos, respectively. The images are not gamma corrected, so they are suitable for rendering, but look too dark and contrasty in image viewers.
glossiness.tiff contains the glossiness value discussed in the paper, i.e. the inverse square root of the Blinn exponent. So in order to get a Blinn exponent, use the formula blinn_exp = 1/(g*g), where g is the value from the image file, scaled to the range [0,1]. The intended BRDF is a normalized (energy conserving) Blinn-Phong, with the illumination angle cosine absorbed (so that the reflection should not darken at low angles), and using a Schlick Fresnel term as described in the paper.
normal.tiff contains the normal map as unit vectors scaled to the range [0,1].
kurtosis.tiff contains the kurtosis, scaled such that the true value is obtained by k*100+1, where k is the value in the file in the range [0,1]. The glossiness values are reasonable for single lobes too, so using the two-lobe kurtosis model is optional.
Please include a citation to our paper if you use these maps in an academic research paper. For other uses, we ask you to link to the project webpage, and include the text "Material models courtesy of Miika Aittala, Tim Weyrich, and Jaakko Lehtinen".